ERYSIPHEAE. 



171 



The operation is done by hand or by special implement. One 

 of the best known of these is the "Sulphur Puff." This 

 consists of a brush with a hollow stem to contain flowers of 

 sulphur, the end of the stem being perforated to allow the 

 sulphur to escape on to the plant. Sulphuring must be 

 carried out during dry weather to prevent the powder being 

 washed away. It has also to be frequently repeated, so that 

 young growing shoots, flowers, fruits, leaves, and all parts 

 liable to attack, may be kept well dusted. Sulphur prevents 

 germination of conidia on the leaves ; it also kills the 

 mycelium, while the plant itself remains uninjured. 



Besides sulphuring, various copper solutions give very good 

 results, while at the same time, they act as a preventive 

 against the false mildews {Plasmopara, Peronospora,, etc.). 



Sphaerotheca. 



Perithecia spherical with thread-like appendages; they contain 

 one spherical ascus with eight colourless oval ascospores. 



Fio. 68. — Rose-mildew. Sphaerotheca pannosa. The fungus forms a white mealj- 

 coating on the leaf, especially on the lower side ; the leaves are alsiO more or less 

 curled up. (v. Tubeuf phot.) 



